Intrinsically conductive polymers (ICPs) have been studied since at the latest 1970's. The term "intrinsically conductive polymer" refers to organic polymers containing polyconjugated bond systems such as double or triple bonds and aromatic rings which have been doped with electron donor dopants or electron acceptor dopants to form a charge transfer complex having an electrical conductivity of at least about 10.sup.-8 S/cm by the four-in-line probe method. Examples of such polymers are polyaniline, polypyrrole, polyacetylene, polythiophene, and the like.
A good overall review of intrinsically conductive polymers, their synthesis, chemical structure and processing is to be found in "Synthetic Metals", volumes 17-19 (1987), 28-30 (1989) and 40-42 (1991).
The term polyaniline covers a whole range of polymers made from aniline and aniline derivatives. The term "doped" polyaniline as used herein is understood to refer to the conductive emeraldine salt form of polyaniline as opposed to the neutral emeraldine base form which is non-conductive. The neutral form of the polymer can be doped (protonated) by protonic acids, to give the doped polymer.
Processing of ICPs has been limited due to their inherent properties. They are infusible and insoluble in most solvents in their doped (conductive) form. Several techniques have been suggested for improving their solubility and processing. These include synthesis of substituted polymers and graft polymers. These techniques have generally yielded polymers with low conductivity and low solubility in their undoped (non-conductive) and doped (conductive) forms. Blends of ICPs are suggested in U.S. Pat. Nos. 4,935,164 and 4,929,388, PCT Application Nos. WO 89/02155, WO 90/10297 and WO 89/01694, and European Patent Application 0421814 A2 and British Patent No. 2,214,511, which present a generally useful process for making a variety of articles.
Several solution processing techniques have been described in the art for preparing films from conductive polymers such as polyaniline. An example of this is found in U.S. Pat. No. 4,983,322.
However, this prior art does not disclose conductive compositions suitable for making thin and/or transparent films with good adhesion to the material which is coated, and which are also tough and scratch resistant, and which retain their conductivity when exposed to common cleaning solvents such as water, alcohols and detergents. All of these attributes are required for applications such as antistatic packaging for electronic components, other electronic applications and the like.